Newsday August 12, 2006
Looking for liquids
The technology exists to detect liquids - and in some cases, more specifically, liquid explosives - in airline baggage. But don't expect to see it widely used at the nation's airports very soon.
One method involves a variation on traditional X-ray technology, while another works by bombarding luggage with neutrons to produce gamma rays.
The first method uses "backscatter" X-rays, which are employed now to screen passengers at some airports. The rays help pick out organic materials such as many explosives or drugs, even when hidden within a complex setting. This kind of equipment, made by American Science and Engineering Inc., has been used also to spot people entering the country illegally. The organic material turns up on screen as a bright white, although a safe liquid could not be distinguished from a dangerous one.
OSI Systems Inc. says its thermal neutron analysis equipment can identify liquid explosives, or any other substances, by bouncing neutrons off a package and then reading the resulting gamma rays. The system contains a database of gamma-ray readings for dangerous substances.
Peter Kant of OSI said there had been a lot of government interest in the company's products, and that the Defense Department was testing some now.
Ann Davis, a spokeswoman for the Transportation Security Administration, said the TSA has been testing equipment to detect bottled liquids since October at about a half-dozen airports. She could not say when such equipment would be deployed.
A better X-ray
X-ray photons scatter differently when they encounter different types of materials. Backscattered X-rays from organic material are displayed as light on a monitor.
Many backscattered X-rays excape fromw organic material
X-rays interact with the electrons in the block of plastic
Detector
Converts the X-rays to an electrical current that is proportional to the X-ray intensity.
LIQUID EXPLOSIVES
Nitroglycerine is one of the most powerful explosives known. Its detonation generates gases that would occupy more than 1,200 times the original volume at room temperature
SOURCE: GLOBALSECURITY.ORG
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